The present invention relates to combinations of polyalphaolefin oils and tackifiers.
Tackifiers may be commonly used in adhesive systems in combination with one or more natural or synthetic elastomers, and/or other ingredients, such as plasticizers, waxes, fillers, and/or antioxidants. Tackifiers are generally either solid or liquid at room temperature and generally have corresponding high or low softening points. The performance of these tackifiers may also vary according to softening point.
High softening point tackifiers increase the softening point of the adhesive formulation and are easily handled. These tackifiers may also have softening points greater than about 80° C. and are solid at or near room temperature (around 20° C.-25° C.). Lower softening point tackifiers are liquid at room temperature, with softening points generally less than about 25° C. Because they are liquid they may be more difficult to handle, but they may also provide the benefits of decreasing the softening point and the glass transition temperature (Tg) of the adhesive.
Medium softening point (MSP) tackifiers may generally be semi-solid materials at room temperature. Although they appear solid, they will flow over time. Such resins have softening points ranging from about 25-80° C., more likely 35-65° C., and more likely within the range of 50-60° C.
Adhesive formulations incorporating MSP tackifiers have lower volatilities than those formulated with a liquid resin and/or plasticizing oil, and can be applied over a broader range of temperatures than similar systems formulated with normally liquid and/or normally solid resins and/or processing oils. In addition, aging studies indicate that the adhesives incorporating MSP tackifiers bleed less and stain less than adhesive formulated with conventional tackifiers and conventional plasticizers.
Control of the softening point is important in the production of tackifiers. The softening point of the tackifying resin is generally determined by the stripping conditions. Targeting a specific softening point while maintaining the resin properties may be difficult. It would be beneficial to find an alternate and less difficult method to target and control the softening point of the tackifier, without losing any of the tackifier properties.
Alternatively, other routes to manufacture MSP resins have been considered and disclosed herein are combinations of one or more conventional tackifiers and one or more polyalphaolefin oils (PAO(s)). The use of certain PAOs lowers the softening point characteristics of the tackifier, which can be controlled by varying the amount or type of PAO selected. This allows tackifier manufacturers and adhesive formulators to target a specific softening point without the difficulties normally encountered during manufacturing or the drawbacks associated with using conventional plasticizers or processing oils.